1. Field of the Invention
The present invention relates to the formation and use of bioresorbable calcium phosphosilicate nanoparticles bioconjugated to molecules that selectively target cells in vitro and in vivo.
2. Description of the Art
The early diagnosis of cancer is the critical element in successful treatment and long term favorable patient prognosis. The high mortality rate, in particular, for pancreatic cancer is primarily attributed to the tendency for late diagnoses as symptoms typically occur after the disease has metastasized as well as the lack of effective systemic therapies. For breast cancer, late diagnosis is often associated with the lack of timely sensitive imaging modalities. The promise of nanotechnology is presently limited by inability to simultaneously seek, treat, and image cancerous lesions.
Despite many new advances in the arsenal of antineoplastic agents, drug resistant, highly metastatic cancers continue to ravage patients21. As examples, breast cancer is still the second leading cause of death in American women with an estimated 192,370 cases diagnosed in 2009. In this year alone, about 40,610 women will die from breast cancer in the United States. Pancreatic cancer is the fourth leading cause of cancer related deaths in the United States. Approximately 42,470 Americans were diagnosed with pancreatic cancer in the past year, and nearly 100% will succumb to this disease21. It is clear that new modalities must be developed that have the capabilities to both improve diagnosis and treatment of cancers. The term “theranostic” has been coined to describe modalities that can simultaneously diagnose and treat.
As described in U.S. patent application Ser. Nos. 10/835,520 and 11/142,913, calcium phosphosilicate nanoparticles (CPNPs) have been engineered to be a resorbable non-toxic vehicle for the delivery of a diversity of therapeutic and imaging agents in biological systems1-4. Previous studies have shown that encapsulation within CPNPs improved the lifetime and quantum properties of fluorescent dyes1, 4. Initial in vivo imaging trials demonstrated that CPNPs, functionalized with polyethylene glycol (PEG) moieties, accumulated within solid tumors via an enhanced permeation retention (EPR) effect2. While EPR serves as an effective passive targeting strategy, particular interest lies in the ability to actively target cancerous cells to deliver antineoplastic agents, thereby decreasing effective dosage and limiting off-target toxicity.
CPNPs are nontoxic, colloidally stable, resorbable, non-aggregated nanoscale vehicles that deliver chemotherapeutics, gene therapy, and imaging agents. Two exciting aspects of CPNPs as drug delivery vehicles include enterohepatic biliary excretion that minimizes hepatic toxicity and pH-triggered release of active agents. At pH 7.4, the CPNPs are sparingly soluble, but the CPNPs dissolve in the late stage endolysosomes at pH 4 to 51,4. The pH response of CPNPs has two distinct advantages. First, it permits a decrease in the effective dose of chemotherapeutic drugs, which are often toxic, required for optimal therapeutic benefit by increasing the efficiency of drug delivery into cancer cells3. Second, sequestering the drug in the CPNPs decreases the effective concentration of free drug present in the extracellular fluid where the pH is maintained at approximately 7.4 by physiological buffers. This compartmentalization feature for drug delivery is a distinct advantage since acute systemic toxicity to normal cells is limited. Moreover, off site cytotoxicity may be further ameliorated with target and tissue-specific CPNPs.
Scientific investigations have identified cancer cell specific markers with unique phenotypes that can be exploited to target tumors as will be described in this patent document. Of particular interest is the prevalence of transferrin receptors (CD71) on cancerous cells, including breast cancer5-9. The transferrin receptor is responsible for transporting iron, via interaction with transferrin, into cells as demanded by metabolic need5, 6 Accordingly, transferrin receptors are found predominately on proliferating cells with elevated metabolic levels, including many cancerous cells, as well as brain capillary endothelial cells, and hematopoietic cells10, 11. In a manner similar to CD71, gastrin receptors have a predominate prevalence within certain tissues, specifically the gastrointestinal and central nervous systems12-14. The hormone gastrin binds to a family of G-protein-coupled receptors, also known as the cholecystokinin-2 (CCK2 or CCK-B) receptor family14, 15, and is typically known as a key mediator of stomach acidity16 and growth of the gastrointestinal tract17. Intriguingly, CCK2 receptor expression is often increased in many cases of gastrointestinal cancer14, 18 including pancreatic cancer19 and, in particular, an increase in expression of a specific splice variant (CCK2i4sv or CCK-C) of the receptor20.
The inventive bioconjugated particles and bioconjugation approaches taught in this patent document may also be used with non-solid tumors. Leukemia is one of the most common and aggressive adult cancers as well as the most prevalent childhood cancer. Leukemia stem cells (LSCs) have been hypothesized to be responsible for cancer development, relapse, and resistance to treatment, and new therapeutics targeting these cellular populations are urgently needed. Recently, studies have indicated that LSCs reside within a lineage −Sca-1+ CD117 cellular population in human patients and animal models of chronic myeloid leukemia (CML) and therefore present a target for intervention.
Accordingly, as outlined above, there is a significant medical need in the field of disease treatment for nanoparticle compositions capable of targeted systemic delivery of imaging and/or therapeutic agents as well as imaging and treatment methods employing such nanoparticles.